David Louis and his group at MGH have had a long-standing commitment to providing detailed pathological assessment of human and experimental brain tumors. The core will interface with all of the proposed projects. The specific aims and services provided include: 1. To provide the infrastructure and technical expertise for processing of all histological samples for this PPG. 2. To provide neuropathology expertise for the diagnosis of mouse gliomas. 3. To provide histology services for cutting of tissue sections for ISH assays (note: this activity was to have been conducted by the high-throughput in situ core that has been removed from this revised application). 4. To provide the technical expertise for immunohistochemical assays for standard markers and candidate genes. 5. To generate high-quality tissue microarrays of mouse gliomas with the goal of cross-species validation. 6. To provide the technical expertise for in situ FISH. 7. To provide the infrastructure and technical expertise for laser micro-dissection. 8. To provide the infrastructure and technical expertise for image analyses.